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Definition df-r1 7452
Description: Define the cumulative hierarchy of sets function, using Takeuti and Zaring's notation ( R1). Starting with the empty set, this function builds up layers of sets where the next layer is the power set of the previous layer (and the union of previous layers when the argument is a limit ordinal). Using the Axiom of Regularity, we can show that any set whatsoever belongs to one of the layers of this hierarchy (see tz9.13 7479). Our definition expresses Definition 9.9 of [TakeutiZaring] p. 76 in a closed form, from which we derive the recursive definition as theorems r10 7456, r1suc 7458, and r1lim 7460. Theorem r1val1 7474 shows a recursive definition that works for all values, and theorems r1val2 7525 and r1val3 7526 show the value expressed in terms of rank. Other notations for this function are R with the argument as a subscript (Equation 3.1 of [BellMachover] p. 477),  _V with a subscript (Definition of [Enderton] p. 202), M with a subscript (Definition 15.19 of [Monk1] p. 113), the capital Greek letter psi (Definition of [Mendelson] p. 281), and bold-face R (Definition 2.1 of [Kunen] p. 95). (Contributed by NM, 2-Sep-2003.)
Assertion
Ref Expression
df-r1  |-  R1  =  rec ( ( x  e. 
_V  |->  ~P x ) ,  (/) )

Detailed syntax breakdown of Definition df-r1
StepHypRef Expression
1 cr1 7450 . 2  class  R1
2 vx . . . 4  set  x
3 cvv 2801 . . . 4  class  _V
42cv 1631 . . . . 5  class  x
54cpw 3638 . . . 4  class  ~P x
62, 3, 5cmpt 4093 . . 3  class  ( x  e.  _V  |->  ~P x
)
7 c0 3468 . . 3  class  (/)
86, 7crdg 6438 . 2  class  rec (
( x  e.  _V  |->  ~P x ) ,  (/) )
91, 8wceq 1632 1  wff  R1  =  rec ( ( x  e. 
_V  |->  ~P x ) ,  (/) )
Colors of variables: wff set class
This definition is referenced by:  r1funlim  7454  r1fnon  7455  r10  7456  r1sucg  7457  r1limg  7459
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